The general utility of a rag or string mop combined with scrubbing units on the mop head has been demonstrated by a variety of patents for over 80 years. Among the inventions have been relatively light-duty attachments either requiring modification of the mop holders as in Neumann patent, U.S. Pat. No. 2,683,886 and McLaughlin, Ser. No. 937,007; or disengagement of the mop clamping means at installation and removal of the scrubbing unit, or a part thereof, as in Held, Ser. Nos. 732,743 and 732,744; Wilson, Ser. No. 701,657; Dryden, U.S. Pat. No. 3,167,798; and Paul, U.S. Pat. No. 2,133,148. Such combination mop and scrubbing units have undoubtedly been of value in increasing the efficiency of the person cleaning floors and decks. However, due to the nature of the work and the need to exert much effort in scrubbing dirty areas, there is a need for a rugged heavy duty quick connect and disconnect scrubbing unit for mop holders. The ease of removal and subsequent installation of such a unit is also an important factor in allowing quick replacement of worn-out or gummed up units.